This invention relates to a suspension clamp for electric overhead cables having multiple support points for the inserted overhead cable and a cable through which may be suspended by a hinged joint from an insulator chain.
In the design of suspension clamps, care must be taken to keep the stressing of the overhead cable as low as possible. More especially, the alternating bending stresses which are caused by oscillations of the conductors of the overhead cable between adjacent suspension clamps must be kept as low as possible, because these stresses reduce the life of the overhead cable. The magnitude of such alternating bending stresses depend upon the construction of the suspension clamp. By providing a hinged suspension for the cable through, it is possible to reduce the alternating bending stresses at the outlet points of the cable trough by almost one half as compared with the alternating stresses generated when a rigidly suspended cable trough is utilized.
In order to further reduce the alternating bending stresses on the cable, suspension clamps have been developed which support the overhead cable at two or more longitudinally spaced points. In prior art clamps of this type, the supporting devices are linked together by levers, in order to obtain as far as possible uniform pressure at all supporting points, but the cost of constructing such a suspension clamp is high and the parts of such a clamp are movable relative to each other causing considerable wear. Owing to the distances between the individual supporting devices, which distances are often quite large, the moment of inertia of such a suspension clamp becomes very large, which is undesirable in view of the resulting oscillation properties.
It has also been proposed that the suspended overhead cable be reinforced in the area of its suspension points by prefabricated wire coils. These wire coils may be placed resiliently around the cable to provide an elastic support for the cable but the suspension clamp must then be provided with a cable channel which is considerably larger in diameter than would be necessary for directly gripping the cable. Because of this such a clamp becomes large, heavy and expensive.
The present invention provides a suspension clamp which keeps the alternating bending stresses of the overhead line low but is nevertheless of simple construction and wear-resistant.